In legacy cellular networks like GSM, WCDMA/HSPA, and LTE, one of the design objectives has been to make system information and reference symbols easily available to all User Equipments, UEs, in a broadcast manner. To take the example of LTE, Physical Broadcast Channel, PBCH, continuously transmits system information over the entire cell coverage area, and Synchronization Channel, SCH, and Cell-specific Reference Signal, CRS, are provided constantly over the same area to allow synchronization, channel characterization, and phase reference estimation.
In coming fifth generation, 5G, network deployments whose standardization has recently started, various significant design changes are expected. To provide sufficient link quality at higher frequency bands, large antenna arrays and high-gain beamforming will be employed. To improve network energy efficiency, reduce interference, increase capacity, and ensure forward compatibility, common information broadcast will be minimized. We anticipate that only minimal system information, enough to perform initial system access, will be broadcasted; all additional System Information, SI, will be delivered to individual UEs in a dedicated manner, utilizing beamforming. To the same end, the amount of always-on synchronization and reference signals will be minimized and in cases they are needed, their repetition period will be made as long as possible. No LTE CRS-like signals are expected. Instead, Demodulation Reference Signal, DMRS, will be used for demodulation purposes and different signals to be detected, e.g. for mobility, are only activated when needed and will be self-contained, including sync features.
From these observations, there is a forecast that searching for reference signals when trying to connect to such a system may be troublesome due to the scarce provision of reference signals when the wireless device has no knowledge about transmissions in the new RAT.